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<pre><span class="sourceLineNo">001</span>package imagingbook.calibration.zhang;<a name="line.1"></a>
<span class="sourceLineNo">002</span><a name="line.2"></a>
<span class="sourceLineNo">003</span>import org.apache.commons.math3.linear.MatrixUtils;<a name="line.3"></a>
<span class="sourceLineNo">004</span>import org.apache.commons.math3.linear.RealMatrix;<a name="line.4"></a>
<span class="sourceLineNo">005</span>import org.apache.commons.math3.linear.RealVector;<a name="line.5"></a>
<span class="sourceLineNo">006</span><a name="line.6"></a>
<span class="sourceLineNo">007</span>import imagingbook.calibration.zhang.util.MathUtil;<a name="line.7"></a>
<span class="sourceLineNo">008</span>import imagingbook.lib.math.Matrix;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span><a name="line.10"></a>
<span class="sourceLineNo">011</span>/**<a name="line.11"></a>
<span class="sourceLineNo">012</span> * This class defines methods for estimating the extrinsic camera parameters<a name="line.12"></a>
<span class="sourceLineNo">013</span> * from multiple homographies.<a name="line.13"></a>
<span class="sourceLineNo">014</span> * <a name="line.14"></a>
<span class="sourceLineNo">015</span> * @author W. Burger<a name="line.15"></a>
<span class="sourceLineNo">016</span> *<a name="line.16"></a>
<span class="sourceLineNo">017</span> */<a name="line.17"></a>
<span class="sourceLineNo">018</span>public class ExtrinsicViewEstimator {<a name="line.18"></a>
<span class="sourceLineNo">019</span>        <a name="line.19"></a>
<span class="sourceLineNo">020</span>        static boolean beVerbose = false;<a name="line.20"></a>
<span class="sourceLineNo">021</span>        <a name="line.21"></a>
<span class="sourceLineNo">022</span>        private final RealMatrix A_inv;<a name="line.22"></a>
<span class="sourceLineNo">023</span>        <a name="line.23"></a>
<span class="sourceLineNo">024</span>        /**<a name="line.24"></a>
<span class="sourceLineNo">025</span>         * The only constructor.<a name="line.25"></a>
<span class="sourceLineNo">026</span>         * @param A the 3 x 3 matrix with intrinsic camera parameters<a name="line.26"></a>
<span class="sourceLineNo">027</span>         */<a name="line.27"></a>
<span class="sourceLineNo">028</span>        protected ExtrinsicViewEstimator(RealMatrix A) {<a name="line.28"></a>
<span class="sourceLineNo">029</span>                this.A_inv = MatrixUtils.inverse(A);<a name="line.29"></a>
<span class="sourceLineNo">030</span>        }<a name="line.30"></a>
<span class="sourceLineNo">031</span>        <a name="line.31"></a>
<span class="sourceLineNo">032</span>        /**<a name="line.32"></a>
<span class="sourceLineNo">033</span>         * Estimates the extrinsic camera parameters for a sequence of homographies.<a name="line.33"></a>
<span class="sourceLineNo">034</span>         * @param homographies a set of homographies given as 3 x 3 matrices<a name="line.34"></a>
<span class="sourceLineNo">035</span>         * @return the sequence of extrinsic camera parameters (views), one view for each homography<a name="line.35"></a>
<span class="sourceLineNo">036</span>         */<a name="line.36"></a>
<span class="sourceLineNo">037</span>        protected ViewTransform[] getExtrinsics(RealMatrix[] homographies) {<a name="line.37"></a>
<span class="sourceLineNo">038</span>                final int M = homographies.length;<a name="line.38"></a>
<span class="sourceLineNo">039</span>                ViewTransform[] views = new ViewTransform[M];<a name="line.39"></a>
<span class="sourceLineNo">040</span>                //ExtrinsicViewEstimator eve = new ExtrinsicViewEstimator(A);<a name="line.40"></a>
<span class="sourceLineNo">041</span>                for (int i = 0; i &lt; M; i++) {<a name="line.41"></a>
<span class="sourceLineNo">042</span>                        views[i] = estimateViewTransform(homographies[i]);<a name="line.42"></a>
<span class="sourceLineNo">043</span>                }<a name="line.43"></a>
<span class="sourceLineNo">044</span>                return views;<a name="line.44"></a>
<span class="sourceLineNo">045</span>        }<a name="line.45"></a>
<span class="sourceLineNo">046</span>        <a name="line.46"></a>
<span class="sourceLineNo">047</span>        private ViewTransform estimateViewTransform(RealMatrix H) {<a name="line.47"></a>
<span class="sourceLineNo">048</span>                RealVector h0 = H.getColumnVector(0);<a name="line.48"></a>
<span class="sourceLineNo">049</span>                RealVector h1 = H.getColumnVector(1);<a name="line.49"></a>
<span class="sourceLineNo">050</span>                RealVector h2 = H.getColumnVector(2);<a name="line.50"></a>
<span class="sourceLineNo">051</span><a name="line.51"></a>
<span class="sourceLineNo">052</span>                double lambda = 1 / A_inv.operate(h0).getNorm();<a name="line.52"></a>
<span class="sourceLineNo">053</span>                if (beVerbose) {<a name="line.53"></a>
<span class="sourceLineNo">054</span>                        System.out.format("lambda = %f\n", lambda);<a name="line.54"></a>
<span class="sourceLineNo">055</span>                }<a name="line.55"></a>
<span class="sourceLineNo">056</span><a name="line.56"></a>
<span class="sourceLineNo">057</span>                // compute the columns in the rotation matrix<a name="line.57"></a>
<span class="sourceLineNo">058</span>                RealVector r0 = A_inv.operate(h0).mapMultiplyToSelf(lambda);<a name="line.58"></a>
<span class="sourceLineNo">059</span>                RealVector r1 = A_inv.operate(h1).mapMultiplyToSelf(lambda);<a name="line.59"></a>
<span class="sourceLineNo">060</span>                RealVector r2 = MathUtil.crossProduct3x3(r0, r1);<a name="line.60"></a>
<span class="sourceLineNo">061</span>                RealVector t  = A_inv.operate(h2).mapMultiplyToSelf(lambda);<a name="line.61"></a>
<span class="sourceLineNo">062</span>                <a name="line.62"></a>
<span class="sourceLineNo">063</span>                if (beVerbose) {<a name="line.63"></a>
<span class="sourceLineNo">064</span>                        System.out.println("r1 = " + Matrix.toString(r0.toArray()));<a name="line.64"></a>
<span class="sourceLineNo">065</span>                        System.out.println("r2 = " + Matrix.toString(r1.toArray()));<a name="line.65"></a>
<span class="sourceLineNo">066</span>                        System.out.println("t = " + Matrix.toString(t.toArray()));<a name="line.66"></a>
<span class="sourceLineNo">067</span>                }<a name="line.67"></a>
<span class="sourceLineNo">068</span>                <a name="line.68"></a>
<span class="sourceLineNo">069</span>                RealMatrix R = MatrixUtils.createRealMatrix(3, 3);<a name="line.69"></a>
<span class="sourceLineNo">070</span>                R.setColumnVector(0, r0);<a name="line.70"></a>
<span class="sourceLineNo">071</span>                R.setColumnVector(1, r1);<a name="line.71"></a>
<span class="sourceLineNo">072</span>                R.setColumnVector(2, r2);<a name="line.72"></a>
<span class="sourceLineNo">073</span>                if (beVerbose) {<a name="line.73"></a>
<span class="sourceLineNo">074</span>                        System.out.println("Rinit = \n" + Matrix.toString(R.getData()));<a name="line.74"></a>
<span class="sourceLineNo">075</span>                }<a name="line.75"></a>
<span class="sourceLineNo">076</span>                                <a name="line.76"></a>
<span class="sourceLineNo">077</span>//              // the R matrix is probably not a real rotation matrix.  So find<a name="line.77"></a>
<span class="sourceLineNo">078</span>//              // the closest real rotation matrix<a name="line.78"></a>
<span class="sourceLineNo">079</span>//              RealMatrix R = MathUtil.approximateRotationMatrix(R);   // not needed, View takes care of this<a name="line.79"></a>
<span class="sourceLineNo">080</span>                        <a name="line.80"></a>
<span class="sourceLineNo">081</span>                // assemble the complete view transformation [R|T]:<a name="line.81"></a>
<span class="sourceLineNo">082</span>//              RealMatrix RT = MatrixUtils.createRealMatrix(3, 4);<a name="line.82"></a>
<span class="sourceLineNo">083</span>//              RT.setSubMatrix(R.getData(), 0, 0);<a name="line.83"></a>
<span class="sourceLineNo">084</span>//              RT.setColumnVector(3, t);<a name="line.84"></a>
<span class="sourceLineNo">085</span>                <a name="line.85"></a>
<span class="sourceLineNo">086</span>                ViewTransform view = new ViewTransform(R, t);<a name="line.86"></a>
<span class="sourceLineNo">087</span>                return view;<a name="line.87"></a>
<span class="sourceLineNo">088</span>        }<a name="line.88"></a>
<span class="sourceLineNo">089</span>        <a name="line.89"></a>
<span class="sourceLineNo">090</span>}<a name="line.90"></a>




























































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